How much of a difference will re-curving my dizzy to my cam specs make.
Is the diffrence very noticeable between done and not, what do they need to know to re-curve the dizzy for me.
I have a 308 with a nice lift cam, are there any places that are really good at this procedure in melb.
Is there anything i should ask them to do when i get it done.
Cheers
JNR_ATE
RE-CURVING MY DIZZY
Started by
_JNR_ATE_
, Apr 09 2006 05:46 PM
7 replies to this topic
#2
_conceptss_
_conceptss_
-
- Guests
Posted 10 April 2006 - 12:10 AM
Defineately noticeable and important .Call IC&E Ignitions in Cheltenham (Melb.) They'll ask you about your car,engine,budget and let you know what your options are.
#3
_devilsadvocate_
_devilsadvocate_
-
- Guests
Posted 10 April 2006 - 11:11 AM
I have no experience with ICE, but suggest that recurving a dizzy exactly to a cam and carby needs some exacting engineering and calibration on a dyno. ie the amount of vac your system pulls at different throttle loads and rpm needs to be measured if this work is going to be really effective. If it was going to be done properly the bill would need to be +$500. Ask what you are getting for the money.
Typically recurving a dizzy just means putting stronger or weaker springs in it for the mechanical advance and changing the shift position on the vac diaphram to control the amount of vac advance.
Typically recurving a dizzy just means putting stronger or weaker springs in it for the mechanical advance and changing the shift position on the vac diaphram to control the amount of vac advance.
#4
knoath
-
- Members
-
- 2,036 posts
far.... FAR
- Location:Melbourne, Northern Subs
- Joined: 09-November 05
Posted 11 April 2006 - 05:48 AM
Hey JNR ATE, try Performance Distributers in Bundoora (can't remember the street name), but about $130 done.
#5
_JNR_ATE_
_JNR_ATE_
-
- Guests
Posted 11 April 2006 - 12:45 PM
Great thanks Knoath, spoke to ICE and they quoted me $150 + pendin gon dizzy condition. had to wait a few weeks a swell.
Cheers
JNR_ATE
Cheers
JNR_ATE
#6
knoath
-
- Members
-
- 2,036 posts
far.... FAR
- Location:Melbourne, Northern Subs
- Joined: 09-November 05
Posted 11 April 2006 - 01:36 PM
OK JNR ATE, the number is.... 9467-5028
16 Monckton Road Bundoora, a drop punt from Plenty Rd, 1st on left as you enter Grimshaw St.
16 Monckton Road Bundoora, a drop punt from Plenty Rd, 1st on left as you enter Grimshaw St.
#7
Dangerous
-
- Members
-
- 948 posts
Forum Fixture
- Location:Adelaide, SA
- Joined: 14-November 05
Posted 12 April 2006 - 12:51 PM
JNR_ATE, for $150, I'd be expecting to see either a before and after dyno curve, or some details about what they've actually done to your distributor. If they're just going to lighten the mech advance springs a bit to give you more advance, then that's not worth $150, and may put you in pinging territory. If on the other hand, they're going to sit down and calculate max safe advance on a few points on the rev range, based on compression ratio, cam specs, carb etc, then that should be a much better and more accurate result, and worth $150. Make sure you know which one they're doing for your hard earned cash.
Very accurate dizzy recurving requires a bit of time on a dyno to map the best advance without pinging across the torque curve. Not cheap.
For what it's worth, I plonked a VK Brock electronic distributor in one of my engines, which was a 308 with stock Qjet, blue motor inlet manifold, Yella Terra heads and mild hydraulic TQ20 cam, extractors, and got it dynoed. The dyno operator, who really knws what he's about said that the advance curve of the stock dizzy was fine for my setup, and that any further recurving would probably be a waste of time and my money.
Very accurate dizzy recurving requires a bit of time on a dyno to map the best advance without pinging across the torque curve. Not cheap.
For what it's worth, I plonked a VK Brock electronic distributor in one of my engines, which was a 308 with stock Qjet, blue motor inlet manifold, Yella Terra heads and mild hydraulic TQ20 cam, extractors, and got it dynoed. The dyno operator, who really knws what he's about said that the advance curve of the stock dizzy was fine for my setup, and that any further recurving would probably be a waste of time and my money.
#8
Dr Terry
-
- Moderators
-
- 3,276 posts
Technical + Numbers Guru + Moderator
- Location:Eastwood (Sydney) NSW
- Joined: 13-November 05
Posted 12 April 2006 - 03:43 PM
Hi Guys.
What devilsadvocate & Dangerous are saying is dead right, but the guys with years of experience on the dyno have this information already, as they've done it all before.
The important part of dizzy recurving (I do it myself), is the total mechanical advance.
Say you have a Holden 6-cylinder & you want to match the dizzy to the camshaft. The ideal max advance is 38 degrees, this is fact, regardless of the cam profile, it's a factor of the wedge shaped combustion chamber design. The wilder the cam (ie more duration) then the more initial advance is required. A stock cam is happy with 6 degrees initial, then 32 degrees is required in centrifugal advance (38 minus 6). If you have say a 35/70 cam it will need around 12 to 14 degrees initial timing, to keep it happy at idle, because of the lost low down torque & vacuum. This means that the centrifugal advance in the dizzy only needs to move 24 degrees (38 minus 14). So basically the bigger the cam, then the more initial that is required & the less that is required inside the dizzy to keep the same total advance.
The actual rate of advance (the springs) & the amount of vacuum advance, can be adjusted accordingly, but these are of minor consequence when compared to the total advance at WOT & full load. I hope I haven't over-simplified it, but that's the basics.
If your in Melbourne, a good guy to see is Dick O'Keefe at Performance Ignition (03) 9872-3644
Dr Terry.
What devilsadvocate & Dangerous are saying is dead right, but the guys with years of experience on the dyno have this information already, as they've done it all before.
The important part of dizzy recurving (I do it myself), is the total mechanical advance.
Say you have a Holden 6-cylinder & you want to match the dizzy to the camshaft. The ideal max advance is 38 degrees, this is fact, regardless of the cam profile, it's a factor of the wedge shaped combustion chamber design. The wilder the cam (ie more duration) then the more initial advance is required. A stock cam is happy with 6 degrees initial, then 32 degrees is required in centrifugal advance (38 minus 6). If you have say a 35/70 cam it will need around 12 to 14 degrees initial timing, to keep it happy at idle, because of the lost low down torque & vacuum. This means that the centrifugal advance in the dizzy only needs to move 24 degrees (38 minus 14). So basically the bigger the cam, then the more initial that is required & the less that is required inside the dizzy to keep the same total advance.
The actual rate of advance (the springs) & the amount of vacuum advance, can be adjusted accordingly, but these are of minor consequence when compared to the total advance at WOT & full load. I hope I haven't over-simplified it, but that's the basics.
If your in Melbourne, a good guy to see is Dick O'Keefe at Performance Ignition (03) 9872-3644
Dr Terry.
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users
